Using wheel orientation to determine future heading

ABSTRACT

The technology relates to determining a future heading of an object. In order to do so, sensor data, including information identifying a bounding box representing an object in a vehicle&#39;s environment and locations of sensor data points corresponding to the object, may be received. Based on dimensions of the bounding box, an area corresponding to a wheel of the object may be identified. An orientation of the wheel may then be estimated based on the sensor data points having locations within the area. The estimation may then be used to determine a future heading of the object.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/429,275, filed Feb. 10, 2017, which is now U.S. Pat. No.10,077,047, the disclosure of which is incorporated herein by reference.

BACKGROUND

Autonomous vehicles, such as vehicles that do not require a humandriver, can be used to aid in the transport of passengers or items fromone location to another. Such vehicles may operate in a fully autonomousmode where passengers may provide some initial input, such as a pickupor destination location, and the vehicle maneuvers itself to thatlocation.

Such vehicles are typically equipped with various types of sensors inorder to detect objects in the surroundings. For example, autonomousvehicles may include lasers, sonar, radar, cameras, and other deviceswhich scan and record data from the vehicle's surroundings. Sensor datafrom one or more of these devices may be used to detect objects andtheir respective characteristics (position, shape, heading, speed,etc.). In many cases, such systems are now able to identify the type ofthe object, for instance using cues such as the object size, shape,speed, location, etc. These characteristics can be used to predict whatan object is likely to do for some brief period into the future whichcan be used to control the vehicle in order to avoid these objects.Thus, detection, identification, and prediction are critical functionsfor the safe operation of autonomous vehicle.

BRIEF SUMMARY

Aspects of the disclosure provide a method of determining a futureheading of an object. The method includes receiving, by one or moreprocessors, sensor data including information identifying an object in avehicle's environment and sensor data points corresponding to theobject; identifying, by the one or more processors, an areacorresponding to an expected location of a wheel of the object based onthe sensor data; estimating, by the one or more processors, anorientation of the wheel based on the sensor data points havinglocations within the area; and determining, by the one or moreprocessors, a future heading of the object based on the estimation.

In one example, estimating the orientation includes fitting any of thesensor data points having locations within the area to a first plane. Inthis example, the sensor data further includes a bounding box boundingthe data points corresponding to the object, and estimating theorientation includes determining an angular difference between a secondplane of a side of the bounding box and the first plane. In addition,estimating the orientation of the wheel is further based on sensor datapoints having locations that are outside of the bounding box and withinthe area. In another example, identifying the area is further based on aprior estimated trajectory of the object determined over a period oftime. In this example, identifying the area is further based on a typeof the object. In another example, the method also includes generating anotification based on the future heading and providing the notificationto a passenger of the vehicle indicating that the object is movingtowards the vehicle. In this example, the notification requests that thepassenger take control of one or more of the steering, acceleration, anddeceleration of the vehicle. In another example, the method alsoincludes using the future heading to control the vehicle in anautonomous driving mode. In another example, identifying the area isfurther based on a model of wheel locations. In this example, the sensordata further includes a bounding box bounding the data pointscorresponding to the object, and identifying the area further includesinputting dimensions of the bounding box into the model. In addition oralternatively, the model is based on a fixed wheel radius. In anotherexample, the method also includes receiving an image of the object andanalyzing the image to identify a possible wheel location, and whereinidentifying the area is further based on the possible wheel location.

Another aspect of the disclosure provides a system for predicting thatan object is going to enter into a trajectory of a vehicle. The systemincludes one or more processors configured to receive sensor dataincluding information identifying an object in a vehicle's environmentand sensor data points corresponding to the object; identify an areacorresponding to an expected location of a wheel of the object based onthe sensor data; estimate an orientation of the wheel based on thesensor data points having locations within the area; and determine afuture heading of the object based on the estimation.

In one example, the one or more processors are further configured toestimate the orientation by fitting any of the sensor data points havinglocations within the area to a first plane. In another example, thesensor data further includes a bounding box bounding the data pointscorresponding to the object, and the one or more processors are furtherconfigured to estimate the orientation by determining an angulardifference between a second plane of a side of the bounding box and thefirst plane. In another example, the one or more processors are furtherconfigured to generate a notification based on the future heading andprovide a notification to a passenger of the vehicle indicating that theobject is moving towards the vehicle. In another example, the one ormore processors are further configured to use the future heading tocontrol the vehicle in an autonomous driving mode. In another example,the system also includes the vehicle.

Another aspect of the disclosure provides a non-transitory computerreadable recording medium on which instructions are stored. Theinstructions when executed by one or more processors, cause the one ormore processors to perform a method for predicting that an object isgoing to enter into a trajectory of a vehicle. The method includesreceiving sensor data including information identifying an object in avehicle's environment and sensor data points corresponding to theobject; identifying an area corresponding to an expected location of awheel of the object based on the sensor data; estimating an orientationof the wheel based on the sensor data points having locations within thearea; and determining a future heading of the object based on theestimation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional diagram of an example vehicle in accordance withaspects of the disclosure.

FIGS. 2A-2D are example external views of a vehicle in accordance withaspects of the disclosure.

FIG. 3 is a view of a roadway and vehicles in accordance with aspects ofthe disclosure.

FIG. 4 is a view of a data and a vehicle in accordance with aspects ofthe disclosure.

FIGS. 5A and 5B are example views of a bounding box in accordance withthe disclosure.

FIGS. 6A and 6B are example views of a bounding box and an areacorresponding to an estimated location of a wheel in accordance with thedisclosure.

FIG. 7 is an example of a bounding box, an area corresponding to anestimated location of a wheel, and an estimated plane in accordance withthe disclosure.

FIG. 8 is another view of a data and a vehicle in accordance withaspects of the disclosure.

FIG. 9 is a flow diagram in accordance with aspects of the disclosure.

DETAILED DESCRIPTION

Overview

The technology relates to predicting a future trajectory of an objectand using this information to make a driving decision for an autonomousvehicle. For certain types of objects having wheels, such as vehicles orbicycles, the raw sensor information can be used to identify therelative orientation of the object's front wheel including the object'stire, rim (or hubcap), or both. For example, in a passenger car, a tiremay be large enough to be detected, but for a bicycle, the tire may befairly thin and more difficult to detect. This can then be used todetermine a future trajectory of the object, for instance, by combininginformation about the object's past trajectory or speed with theorientation of the wheel.

The perception system and/or the vehicle's computing devices may useprior observations of the object to predict a future trajectory of theobject. For instance, an object's speed, orientation/heading, location,state (i.e. turn signal, etc.), prior estimated trajectory, may be usedto predict a series of locations and times in the future where theobject is likely to be. Together, these locations and times may form atrajectory for the object for some brief period into the future.

The vehicle's perception system may also identify the location of sensordata points corresponding to an object. This information may be providedby segmentation of the sensor data. Segmentation is the process oflabeling sensor data such that the computing devices know which sensordata points (or vision pixels) correspond to an object. In someinstances, the sensor data may be segmented into bounding boxes whichrepresent estimated dimensions of an object. In addition, the perceptionsystem may provide information identifying sensor data points around theobject, but not specifically associated with the object by thesegmentation. The perception system may also identify and providecharacteristics of the object, such as the object's location,orientation, size, shape, type, direction and speed of movement, etc.

Using the size of the bounding box and/or the dimensions of the object,the vehicle's computing devices may estimate an area corresponding to alocation of a wheel of the object. In order to estimate location of awheel (front or rear) of an object, the vehicle's computing system mayhave access to information identifying expected wheel locations fordifferent vehicle sizes, or in some cases, even vehicle types. Using theexample of the front wheel, generally, unless the object is headingtowards the vehicle's sensors, only one front wheel will be visible tothe sensors, so the location of this front wheel relative to thebounding box can be estimated based on a combination of the heading ofthe object (for instance, from a past trajectory of the object) and theexpected wheel locations (identified using the size of the bounding boxand/or dimensions of the object).

The data points within the area may then be analyzed to identify anaverage orientation of the points in the area. For instance, the datapoints may be fit to a plane using a simple plane fitting algorithm. Thedifference between this plane and the plane of the side of the boundingbox may be estimated to be an orientation of the vehicle's wheel.

Of course, the number of data points within the area will depend uponthe relative positions, distance and angle between the object's frontwheel and the vehicle's sensors. In that regard, the closer the objectis to the vehicle and the more perpendicular the wheel is to thevehicle's sensors, the more sensor data points are likely to be receivedfrom wheel surface and the more accurate the estimation may be.

The estimation may be used as an indication of the curvature of thefuture path of the object or yaw rate of the object. For example,combining the future wheel orientation with the object's speed, atrajectory of the object can be determined. The predicted heading ortrajectory may then be used to make driving decisions for the vehicle.

The features described herein allow a vehicle's computing devices toestimate an orientation of an object's wheels. This may allow thevehicle's computing devices to predict a change in the heading of anobject, before the object even begins to make the heading change. Bydoing so, the vehicle's computing devices can better predict a futurepath or trajectory of the object and thus make better decisions abouthow to control the vehicle.

Example Systems

As shown in FIG. 1, a vehicle 100 in accordance with one aspect of thedisclosure includes various components. While certain aspects of thedisclosure are particularly useful in connection with specific types ofvehicles, the vehicle may be any type of vehicle including, but notlimited to, cars, trucks, motorcycles, busses, recreational vehicles,etc. The vehicle may have one or more computing devices, such ascomputing devices 110 containing one or more processors 120, memory 130and other components typically present in general purpose computingdevices.

The memory 130 stores information accessible by the one or moreprocessors 120, including instructions 132 and data 134 that may beexecuted or otherwise used by the processor 120. The memory 130 may beof any type capable of storing information accessible by the processor,including a computing device-readable medium, or other medium thatstores data that may be read with the aid of an electronic device, suchas a hard-drive, memory card, ROM, RAM, DVD or other optical disks, aswell as other write-capable and read-only memories. Systems and methodsmay include different combinations of the foregoing, whereby differentportions of the instructions and data are stored on different types ofmedia.

The instructions 132 may be any set of instructions to be executeddirectly (such as machine code) or indirectly (such as scripts) by theprocessor. For example, the instructions may be stored as computingdevice code on the computing device-readable medium. In that regard, theterms “instructions” and “programs” may be used interchangeably herein.The instructions may be stored in object code format for directprocessing by the processor, or in any other computing device languageincluding scripts or collections of independent source code modules thatare interpreted on demand or compiled in advance. Functions, methods androutines of the instructions are explained in more detail below.

The data 134 may be retrieved, stored or modified by processor 120 inaccordance with the instructions 132. For instance, although the claimedsubject matter is not limited by any particular data structure, the datamay be stored in computing device registers, in a relational database asa table having a plurality of different fields and records, XMLdocuments or flat files. The data may also be formatted in any computingdevice-readable format.

The one or more processor 120 may be any conventional processors, suchas commercially available CPUs. Alternatively, the one or moreprocessors may be a dedicated device such as an ASIC or otherhardware-based processor. Although FIG. 1 functionally illustrates theprocessor, memory, and other elements of computing devices 110 as beingwithin the same block, it will be understood by those of ordinary skillin the art that the processor, computing device, or memory may actuallyinclude multiple processors, computing devices, or memories that may ormay not be stored within the same physical housing. For example, memorymay be a hard drive or other storage media located in a housingdifferent from that of computing devices 110. Accordingly, references toa processor or computing device will be understood to include referencesto a collection of processors or computing devices or memories that mayor may not operate in parallel.

Computing devices 110 may include all of the components normally used inconnection with a computing device such as the processor and memorydescribed above as well as a user input 150 (e.g., a mouse, keyboard,touch screen and/or microphone) and various electronic displays (e.g., amonitor having a screen or any other electrical device that is operableto display information). In this example, the vehicle includes aninternal electronic display 152 as well as one or more speakers 154 toprovide information or audio visual experiences. In this regard,internal electronic display 152 may be located within a cabin of vehicle100 and may be used by computing devices 110 to provide information topassengers within the vehicle 100.

Computing devices 110 may also include one or more wireless networkconnections 156 to facilitate communication with other computingdevices, such as the client computing devices and server computingdevices described in detail below. The wireless network connections mayinclude short range communication protocols such as Bluetooth, Bluetoothlow energy (LE), cellular connections, as well as various configurationsand protocols including the Internet, World Wide Web, intranets, virtualprivate networks, wide area networks, local networks, private networksusing communication protocols proprietary to one or more companies,Ethernet, WiFi and HTTP, and various combinations of the foregoing.

In one example, computing devices 110 may be an autonomous drivingcomputing system incorporated into vehicle 100. The autonomous drivingcomputing system may capable of communicating with various components ofthe vehicle. For example, returning to FIG. 1, computing devices 110 maybe in communication with various systems of vehicle 100, such asdeceleration system 160, acceleration system 162, steering system 164,signaling system 166, routing system 168, positioning system 170, andperception system 172, and power system 174, for instance a gas ordiesel powered engine or electric motor, in order to control themovement, speed, etc. of vehicle 100 in accordance with the instructions132 of memory 130. Again, although these systems are shown as externalto computing devices 110, in actuality, these systems may also beincorporated into computing devices 110, again as an autonomous drivingcomputing system for controlling vehicle 100.

As an example, computing devices 110 may interact with decelerationsystem 160 and acceleration system 162 in order to control the speed ofthe vehicle. Similarly, steering system 164 may be used by computingdevices 110 in order to control the direction of vehicle 100. Forexample, if vehicle 100 is configured for use on a road, such as a caror truck, the steering system may include components to control theangle of wheels to turn the vehicle. Signaling system 166 may be used bycomputing devices 110 in order to signal the vehicle's intent to otherdrivers or vehicles, for example, by lighting turn signals or brakelights when needed.

Routing system 168 may be used by computing devices 110 in order todetermine and follow a route to a location. In this regard, the routingsystem 168 and/or data 134 may store detailed map information, e.g.,highly detailed maps identifying the shape and elevation of roadways,lane lines, intersections, crosswalks, speed limits, traffic signals,buildings, signs, real time traffic information, vegetation, or othersuch objects and information. In other words, this detailed mapinformation may define the geometry of vehicle's expected environmentincluding roadways as well as speed restrictions (legal speed limits)for those roadways. In addition, this map information may includeinformation regarding traffic controls, such as traffic signal lights,stop signs, yield signs, etc., which, in conjunction with real timeinformation received from the perception system 172, can be used by thecomputing devices 110 to determine which directions of traffic have theright of way at a given location.

The map information need not be entirely image based (for example,raster). For example, the map information may include one or moreroadgraphs or graph networks of information such as roads, lanes,intersections, and the connections between these features. Each featuremay be stored as graph data and may be associated with information suchas a geographic location and whether or not it is linked to otherrelated features, for example, a stop sign may be linked to a road andan intersection, etc. In some examples, the associated data may includegrid-based indices of a roadgraph to allow for efficient lookup ofcertain roadgraph features.

Positioning system 170 may be used by computing devices 110 in order todetermine the vehicle's relative or absolute position on a map or on theearth. For example, the position system 170 may include a GPS receiverto determine the device's latitude, longitude and/or altitude position.Other location systems such as laser-based localization systems,inertial-aided GPS, or camera-based localization may also be used toidentify the location of the vehicle. The location of the vehicle mayinclude an absolute geographical location, such as latitude, longitude,and altitude as well as relative location information, such as locationrelative to other cars immediately around it which can often bedetermined with greater accuracy than absolute geographical location.

The positioning system 170 may also include other devices incommunication with computing devices 110, such as an accelerometer,gyroscope or another direction/speed detection device to determine thedirection and speed of the vehicle or changes thereto. By way of exampleonly, an acceleration device may determine its pitch, yaw or roll (orchanges thereto) relative to the direction of gravity or a planeperpendicular thereto. The device may also track increases or decreasesin speed and the direction of such changes. The device's provision oflocation and orientation data as set forth herein may be providedautomatically to the computing devices 110, other computing devices andcombinations of the foregoing.

The perception system 172 also includes one or more components fordetecting objects external to the vehicle such as other vehicles,obstacles in the roadway, traffic signals, signs, trees, etc. Forexample, the perception system 172 may include lasers, sonar, radar,cameras and/or any other detection devices that record data which may beprocessed by computing devices 110. In the case where the vehicle is asmall passenger vehicle such as a car, the car may include a laser orother sensors mounted on the roof or other convenient location. Forinstance, a vehicle's perception system may use various sensors, such asLIDAR, sonar, radar, cameras, etc. to detect objects and theircharacteristics such as location, orientation, size, shape, type,direction and speed of movement, etc. The raw data from the sensorsand/or the aforementioned characteristics can be quantified or arrangedinto a descriptive function or vector for processing by the computingdevices 110. As discussed in further detail below, computing devices 110may use the positioning system 170 to determine the vehicle's locationand perception system 172 to detect and respond to objects when neededto reach the location safely.

FIGS. 2A-2D are examples of external views of vehicle 100 having a widthdimension W1 (as shown in FIGS. 2A and 2C), a length dimension L1 (asshown in FIG. 2D), and a height dimension H1 (as shown in FIGS. 2B, 2Cand 2D). As can be seen, vehicle 100 includes many features of a typicalvehicle such as headlights 202, windshield 203, taillights/turn signallights 204, rear windshield 205, doors 206, side view mirrors 208,wheels and wheels 210, and turn signal/parking lights 212. Headlights202, taillights/turn signal lights 204, and turn signal/parking lights212 may be associated with the signaling system 166. Light bar 207 mayalso be associated with the signaling system 166.

Vehicle 100 also includes sensors of the perception system 172. Forexample, housing 214 may include one or more laser devices for having260 degree or narrower fields of view and one or more camera devices.Housings 216 and 218 may include, for example, one or more radar and/orsonar devices. The devices of the perception system 172 may also beincorporated into the typical vehicle components, such astaillights/turn signal lights 204 and/or side view mirrors 208. Each ofthese radar, camera, and lasers devices may be associated withprocessing components which process data from these devices as part ofthe perception system 172 and provide sensor data to the computingdevices 110.

The computing devices 110 may control the direction and speed of thevehicle by controlling various components. By way of example, computingdevices 110 may navigate the vehicle to a destination locationcompletely autonomously using data from the detailed map information,perception system 172, and routing system 168. In order to maneuver thevehicle, computing devices 110 may cause the vehicle to accelerate(e.g., by increasing fuel or other energy provided to the power system174 by acceleration system 162), decelerate (e.g., by decreasing thefuel supplied to the power system 174, changing gears, and/or byapplying brakes by deceleration system 160), change direction (e.g., byturning the front or rear wheels of vehicle 100 by steering system 164),and signal such changes (e.g., by lighting turn signals of signalingsystem 166). Thus, the acceleration system 162 and deceleration system160 may be a part of a drivetrain that includes various componentsbetween a power system 174 of the vehicle and the wheels of the vehicle.Again, by controlling these systems, computing devices 110 may alsocontrol the drivetrain of the vehicle in order to maneuver the vehicleautonomously.

The perception system 172 and/or computing devices 110 may use priorobservations of the object to predict a future trajectory of the object.For instance, an object's speed, orientation/heading, location, state(i.e. turn signal, etc.) may be used to predict a series of locationsand times in the future where the object is likely to be. Together,these locations and times may form a trajectory for the object for somebrief period into the future.

As discussed further below, the perception system 172 may also provide abounding box representing the location of sensor data pointscorresponding to an object. In addition, the perception system mayprovide information identifying all of the points within and, in somecases, also any points within an area around that bounding box.

The data 134 may include a database, table or other organization systemthat relates bounding box sizes or dimensions to expected wheellocations. For example, different bounding boxes may accommodate objectsof different sizes which may have wheels located at different relativepositions. For example, for a size of a side given bounding box, as anexample, 8 feet by 5 feet, the expected wheel location may be measuredfrom a corner of the bounding box corresponding to the front end of theobject and have a predetermined size, as an example 2 feet 4 inches backfrom the corner. In some cases, the expected wheel locations may befurther delineated by specific objecct types, such as, for instance,whether the object is bus, truck, passenger car, motorcycle, bicycleetc. These actual dimensions may be based on actual observed wheellocations on different size and/or types of objects.

Example Methods

In addition to the operations described above and illustrated in thefigures, various operations will now be described. It should beunderstood that the following operations do not have to be performed inthe precise order described below. Rather, various steps can be handledin a different order or simultaneously, and steps may also be added oromitted.

The computing devices 110 may initiate the necessary systems to controlthe vehicle autonomously along a route to the destination location. Forinstance, the routing system 168 may use the map information of data 134to determine a path or route to the destination location that follows aset of the lane segments of map information. The computing devices 110may then maneuver the vehicle autonomously (or in an autonomous drivingmode) as described above along the route towards the destination.

In order to follow the route, the computing devices 110 may periodicallydetermine a trajectory for the vehicle. For example, using the route asa baseline, the computing devices may generate a set of future locationsof the vehicle in order to both follow the route using the detailed mapinformation and avoid close interaction with other road users, such aspedestrians, bicyclists, and pedestrians. These future locations may beused by the computing devices to guide the steering, acceleration and/ordeceleration of the vehicle in order to follow the route.

For instance, FIG. 3 is an example view of vehicle 100 being maneuveredby the computing devices 110 along a roadway 300. In this example,roadway includes northbound lanes 310, 312 and southbound lanes 314,316. Vehicle 100 is traveling in the northbound lane 310 and isapproaching another vehicle 320. Vehicle 320 is traveling in thenorthbound lane 312.

As the vehicle 100 is traveling, the sensors of the perception system172 may detect various objects in the vehicle's environment. FIG. 4 is arepresentation of objects detected by the perception system 172 and theposition of vehicle 100 corresponding to the view of roadway 300 in FIG.3. In this example, the perception system 172 may detect lanes lines401, 402, 403, 404, 405, and 406 which define lanes 410, 412, 414, and416. In this example, lanes 410, 412, 414, and 416 may correspond toeach of northbound lanes 310 and 312 and southbound lanes 314 and 316,respectively. In addition, perception system 172 has also detectedvehicle 320.

For each object, the vehicle's perception system may use segmentation toidentify specific sensor data points corresponding to an object. Thismay also include determining a bounding box representing the dimensionsof that object. This may be achieved using any known segmentation and/orbounding box techniques. For instance, as shown in FIG. 4, the locationof vehicle 320 is represented by bounding box 420 which includes datapoints that the perception system 172 has determined to correspond to anobject. FIG. 5A depicts a top down view of the relative positions ofvehicle 100 and bounding box 420 as shown in FIG. 4. Arrow 510represents the current or observed heading of vehicle 320 and thereforethe heading of bounding box 420. FIG. 5B depicts a side view of thebounding box 420. Arrows 520 and 522 identify the corresponding sides ofthe bounding box 420 of FIGS. 5A and 5B. The distances X, Y, and Zrepresent the width, length and height of the bounding box 420.

The characteristics of the identified objects as well as thesegmentation information identifying the sensor data points (and in somecases, bounding boxes) for those objects may be provided to thecomputing devices 110 by the perception system 172. As an example, thesecharacteristics may include the location (GPS coordinates and/orrelative to the vehicle), size, shape, dimensions, speed, orientation,elevation, type (passenger vehicle, tractor trailer, bicycle,pedestrian), features of the road surface (lane lines, etc.), and more.In addition, the perception system may provide information identifyingsensor data points around the object, but not specifically associatedwith the object according to the segmentation.

The perception system and/or the vehicle's computing devices may useprior observations of the object to predict a future trajectory of theobject. For instance, an object's speed, orientation/heading, location,state (i.e. turn signal, etc.), or prior estimated trajectory may beused to predict a series of locations and times in the future where theobject is likely to be. Together, these locations and times may form atrajectory for the object for some brief period into the future. Withregard to the examples of FIGS. 3 and 4, the perception system 172 maypredict that the vehicle 320 or the object of bounding box 420 maycontinue traveling north following northbound lane 312 or lane 412 basedon the object's prior history of traveling in northbound lane 312 orlane 412.

When the characteristics of an object are determined to correspond to anobject that has a wheel, for instance because it is located in a laneand is of at least a particular size, has a particular shape, is movingat a particular speed, is of a particular type, etc., the computingdevices may attempt to estimate a location of a wheel of the object.Again, this determination may be made by the computing devices 110 onthe basis of the characteristics received from the perception system172.

Using the dimensions of the bounding box and/or the size of the object,the vehicle's computing devices may estimate an area corresponding to alocation of a wheel of the object. In order to estimate location of awheel (front or rear) of an object, the vehicle's computing system mayaccess the expected wheel locations of data 134 and identify an expectedwheel location corresponding to the dimensions (X, Y, and Z) of thebounding box 420. An expected wheel location may correspond to a 2D areasuch as a disc or a 3D volume such as a cylinder with a heightcorresponding to a width of a wheel located at some distance relative toa particular corner of the bounding box. So given the dimensions of thebounding box, the computing devices 110 may identify an area (2D or 3D)of the bounding box where a wheel of the object (vehicle 320) is likelyto be located.

In addition to the dimensions of the bounding box, other characteristicsfrom the perception system 172 may be used to identifying an expectedwheel location from the data 134. As an example, if the bounding box 420is identified as corresponding to a passenger car, the expected wheellocation identified from the data 134 may be different from a situationin which the bounding box 420 is identified as corresponding to a bus orbicycle.

As shown in, FIGS. 6A and 6B, area 610, which represents an expectedwheel location for a front wheel of bounding box 420, is a cylinder. Onecircular end surface 612 of the cylinder is located at or a shortdistance, such as 2 or 3 inches or more or less, outside of surface S ofthe bounding box (the side of the bounding box to which the location ofwheel would correspond as shown in FIG. 6B). In this regard, other datapoints representing objects or surfaces which may have beenintentionally or unintentionally excluded from the bounding box 420, butwhich are still within a short distance of the bounding box, forinstance, 2 or 3 inches or more or less, may also be included in theanalysis in order to avoid missing points which could still correspondto a wheel.

Again, in this example, arrow 620 represents the heading of the boundingbox 420 and thus corresponds to arrow 510 of FIG. 5. In this example,the area may be identified as being a cylinder of radius R and height H,located at a distance D from corner C corresponding to a corner of thebounding box visible to the perception system 172 and closest to thefront of the vehicle according to the heading of the vehicle. As anexample only, for a small passenger vehicle R may be 12.25 inches, H maybe 7.3 inches, and D may be 32.413 inches.

Using the example of the front wheel, generally, unless the object isheading towards the vehicle's sensors, only one front wheel will bevisible to the sensors, so the location of this front wheel relative tothe bounding box can be estimated based on a combination of the headingof the object (for instance from the past trajectory of the object) andthe expected wheel locations (identified using the size of the boundingbox and/or dimensions of the object). In other words, arrow 620(corresponding to arrow 510), representing the heading of the boundingbox 420 (as determined from a past trajectory of the object), can beused to identify the front of the vehicle, assuming that vehiclestypically travel forwards.

The data points within the area may then be analyzed to identify anaverage orientation of the points in the area. For instance, the datapoints may be fit to a plane using a simple plane fitting algorithm.FIG. 7 is a top down view of the bounding box 420 depicting the area610. In this example, the points within area 610 are fit to plane 710.The angular difference between plane 710 and the plane of the surface Sof the bounding box, or angle θ, may be estimated to be an orientationof the front wheel of the object of bounding box 420, here vehicle 320.

The object's past trajectory can also be used to get an idea or estimateof the orientation of the front wheel. For instance, the object's pastheading could be used as a seed (a start angle) when fitting the datapoints to the plane. Alternatively, the past trajectory could be usedalone to determine the orientation of the vehicle's wheel.

Of course, the number of data points within the area will depend uponthe relative positions, distance and angle between the object's frontwheel and the vehicle's sensors. In that regard, the closer the objectis to the vehicle and the more perpendicular the wheel is to thevehicle's sensors, the more sensor data points are likely to be receivedfrom wheel surface and the more accurate the estimation may be.

The estimation may be used as an indication of the curvature of thefuture path of the vehicle (the change in orientation over distance) oryaw rate (the change in orientation over time). For example, combiningthe future wheel orientation with the object's speed, a trajectory ofthe object can be determined. In this regard, the estimation may be usedto determine a future heading for an object, a future trajectory for anobject, or alternatively, increase or decrease a likelihood orconfidence in different future trajectories for an object.

The predicted heading or trajectory may then be used to make drivingdecisions for the vehicle. For instance, when the object is in anadjacent lane, the predicted heading may be a very early indication thatthe object is going to move towards the vehicle's lane. As an example,turning to FIG. 8, where the angle θ is relatively large, such as 15degrees or more or less, this may indicate a future heading or futuretrajectory 810 of the bounding box 420 which takes the object (vehicle320) towards the northbound lane 310. In this example, the futuretrajectory (heading and speed over a future period of time) of thebounding box may indicate that the object will enter into lane 410within a predetermined period of time, for instance 1 second or more orless. In response, the vehicle's computing devices may control thevehicle to speed up, slow down, or even change lanes as appropriate toavoid a collision or even getting too close to vehicle 320. In extremecases, such as where the object appears to be changing headingserratically, the vehicle's computing devices may even notify a passengerof the vehicle to take control of the steering, braking, or accelerationif possible. Alternatively, if the vehicle is being controlled in asemi-autonomous or manual mode, the notification may be provided inorder to assist the driver of the vehicle.

Alternatively, the area may be determined by using a model of wheellocations. In this regard, the size, location, and shape of the boundingbox as well as the locations of the data points, may be used to fit amodel which provides the orientation of the wheel using a simple fixedwheel radius for the wheel or more complex wheel radius that dependsupon the size of the bounding box. In this example, the model may betrained using machine learning where operators mark and identify datapoints corresponding to wheels as positive examples for training datafor the model.

The features described above may relate to laser data points whichprovide distance, direction and intensity information. In this regard,the intensity information may be used as a cue to indicate the outer rimof the wheel (i.e. a black wheel would have low reflectivity andtherefore low intensity). In this regard, the area may be estimatedusing one or more images of the object and thereafter, the laser datamay be used to identify the orientation of the wheel.

Similarly, if the perception system provides camera data, the locationof a black object above the road surface and proximate to the locationof the bounding box may be used as a cue to indicate a location of awheel. In some cases, an image alone may be sufficient to recognize apossible wheel location and even estimate an orientation of a vehicle'swheel, for instance, using a 3D model estimation from two or more imagesof the wheel and/or 3D model data generated for the image using laserdata. Another way to compute wheel orientation from an image may includedetermining the aspect ratio of wheel width and height in the image.This aspect ratio may correspond to a wheel orientation. Combining thiswith the orientation of the object, as determined from other sensordata, image processing of the image or multiple images of the wheel, therelative wheel orientation can be computed.

Estimating the wheel orientation can even be useful for very slow movingand even stopped vehicles. For instance, an object that is ready to moveout of a parking spot may have angled the object's wheels to move out ofthe parking spot, but may not actually have begun moving. Thus, usingthe angle of the wheel to estimate a future trajectory of an object ismore likely to predict accurately the object's trajectory as otherwise,the computing devices would likely predict that the object would remainstationary. In another example, a given vehicle is stopped in anadjacent lane may attempting to change into the lane of the vehicle 100,for instance, because the driver of that car has changed his mind andwants to change his route and use the lane. In such cases, the wideangle of the wheel relative to the side of the given vehicle may providemore information about where the given vehicle is going to go than thegiven vehicle's prior trajectory. Such stationary lane changes orlow-speed lane changes are common cases where the front wheels areangled significantly.

FIG. 8 is an example flow diagram 900 in accordance which may beperformed by one or more processors of one or more computing devices ofa vehicle, such as computing devices 110 of vehicle 100 in order todetermine a future heading of an object. In this example, sensor data,including information identifying a bounding box representing an objectin a vehicle's environment and locations of sensor data pointscorresponding to the object, is received at block 910. An areacorresponding to a front wheel of the object based on the size of thebounding box is identified at block 920. An orientation of the wheel isdetermined based on the sensor data points having locations within thearea at block 930. A future heading of the object is determined based onthe estimation at block 940.

Unless otherwise stated, the foregoing alternative examples are notmutually exclusive, but may be implemented in various combinations toachieve unique advantages. As these and other variations andcombinations of the features discussed above can be utilized withoutdeparting from the subject matter defined by the claims, the foregoingdescription of the embodiments should be taken by way of illustrationrather than by way of limitation of the subject matter defined by theclaims. In addition, the provision of the examples described herein, aswell as clauses phrased as “such as,” “including” and the like, shouldnot be interpreted as limiting the subject matter of the claims to thespecific examples; rather, the examples are intended to illustrate onlyone of many possible embodiments. Further, the same reference numbers indifferent drawings can identify the same or similar elements.

The invention claimed is:
 1. A method of determining a future heading ofan object, the method comprising: receiving, by one or more processors,sensor data including information identifying an object in a vehicle'senvironment and sensor data points corresponding to the object;identifying, by the one or more processors, an area corresponding to anexpected location of a wheel of the object based on the sensor data;estimating, by the one or more processors, an orientation of the wheelbased on the sensor data points having locations that are outside of abounding box including the sensor data points corresponding to theobject and within the area; and determining, by the one or moreprocessors, the future heading of the object based on the estimation. 2.The method of claim 1, wherein estimating the orientation includesfitting any of the sensor data points having locations within the areato a first plane.
 3. The method of claim 2, wherein estimating theorientation includes determining an angular difference between a secondplane of a side of the bounding box and the first plane.
 4. The methodof claim 1, wherein the bounding box represents estimated dimensions ofthe object.
 5. The method of claim 1, wherein the expected location ofthe wheel corresponds to a two dimensional area such as a disc or athree dimensional volume such as a cylinder with a width of the wheellocated at a distance relative to a corner of the bounding box.
 6. Themethod of claim 1, wherein identifying the area is further based on atype of the object.
 7. The method of claim 6, wherein the type of theobject includes a passenger vehicle, a tractor trailer, a bus or abicycle.
 8. A system of determining a future heading of an object, thesystem comprising one or more processors configured to: receive sensordata including information identifying an object in a vehicle'senvironment and sensor data points corresponding to the object; identifyan area corresponding to an expected location of a wheel of the objectbased on the sensor data; estimate an orientation of the wheel based onthe sensor data points having locations that are outside of a boundingbox including the data points corresponding to the object and within thearea; and determine the future heading of the object based on theestimation.
 9. The system of claim 8, wherein the one or more processorsare further configured to estimate the orientation by fitting any of thesensor data points having locations within the area to a first plane.10. The system of claim 9, wherein the one or more processors arefurther configured to estimate the orientation by determining an angulardifference between a second plane of a side of the bounding box and thefirst plane.
 11. The system of claim 8, wherein the bounding boxrepresents estimated dimensions of the object.
 12. The system of claim8, wherein the expected location of the wheel corresponds to a twodimensional area such as a disc or a three dimensional volume such as acylinder with a width of the wheel located at a distance relative to acorner of the bounding box.
 13. The system of claim 8, wherein the oneor more processors are further configured to identify the area based ona type of the object.
 14. The system of claim 13, wherein the type ofthe object is one of a passenger vehicle, a tractor trailer, a bus, or abicycle.
 15. The system of claim 8, wherein the one or more processorsare further configured to use the further heading to control the vehiclein an autonomous driving mode.
 16. The system of claim 8, furthercomprising the vehicle.
 17. A non-transitory computer readable recordingmedium on which instructions are stored, the instructions when executedby one or more processors, cause the one or more processors to perform amethod of determining a future heading of and object, the methodcomprising: receiving sensor data including information identifying anobject in a vehicle's environment and sensor data points correspondingto the object; identifying an area corresponding to an expected locationof a wheel of the object based on the sensor data; estimating anorientation of the wheel based on the sensor data points havinglocations that are outside of a bounding box including the data pointscorresponding to the object and within the area; and determining thefuture heading of the object based on the estimation.
 18. The computerreadable recording medium of claim 17, wherein the method furthercomprises using the future heading to control the vehicle in anautonomous driving mode.
 19. The computer readable recording medium ofclaim 17, wherein the expected location of the wheel corresponds to atwo dimensional area such as a disc or a three dimensional volume suchas a cylinder with a width of the wheel located at a distance relativeto a corner of the bounding box.
 20. The computer readable recordingmedium of claim 17, wherein the bounding box represents estimateddimensions of the object.